This invention relates to a new synthetic fiber of the acrylic series having a superior non-inflammability and moreover, superior in the properties of light-proof, anti-rusting, anti-yellowing from thermal exposure and anti-devitrifying.
Acrylic fibers have many superior chemical and physical properties such as dyeability, touch, light-proof, etc. However, recently demand has increased for textile products, such as those made of acrylic fibers, having non-inflammability properties. Especially as the desired quality of life has increased, demand for protection from fire has increased. There is increased governmental regulation of product safety, especially from easy inflammability of acrylic fibers. For example, since the conventional acrylic fiber has a defect in its non-inflammability, it cannot be used widely as material for, such as, interior products such as curtains and carpets, and for baby's and children's clothes, and clothing for the aged. These products should be non-inflammable.
In order to improve the inferior non-inflammability of acrylic fibers, various techniques have been used in the prior art. For example, known is a method using spinning dope of acrylic resin containing a known non-inflammabilizing agent. In another method, a non-inflammabilizing agent is added by an after treatment. In still another method, a spinning dope containing an acrylic resin and a non-inflammable polymer is used. However, in none of these prior methods has a satisfactory result been yet achieved. For example, when adding a non-inflammabilizing agent, the characteristic properties of acrylic fiber such as touch, etc, are considerably changed for the worse since it is necessary to add a large quantity of non-inflammabilizing agent to obtain sufficient non-inflammability of the acrylic fiber. Moreover, it is impossible to obtain a permanent non-inflammability since the added agent is gradually lost during the dyeing step and with each washing of the fiber. Further, when spinning the polymer mixture, it is difficult to produce a non-inflammable acrylic fiber industrially since it is difficult to retain the dope in a stable uniform state.
Furthermore, an acrylic fiber having a semi-permanent non-inflammability may be obtained by a method which carries out copolymerization of acrylonitrile with a halogen-containing monomer such as, for example, vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, etc. However, in this case, although the non-inflammability of the obtained fiber increases with the increase of the content of halogen in the copolymer, other characteristic properties of acrylic fiber such as anti-devitrifying property, light-proof property, anti-rusting property, durability of whiteness in thermal exposure, and thermal durability etc, correspondingly decrease. Therefore, it is concluded that in the prior art, an acrylic fiber having both superior non-inflammability and other characteristic properties such as anti-devitrifying property, light-proof property, anti-rusting property, anti-yellowing property in thermal exposure and thermal durability has not yet been realized.
Japanese Pat. Pub. No. S.48 (1973)--29502 discloses that the anti-vitrifying property of acrylic fiber becomes inferior until the fiber is completely devitrified if the content of halogen-containing monomer in a copolymer of acrylonitrile and vinyl chloride or in a copolymer of acrylonitrile and vinylidene chloride, from which the fiber is produced, is 20 to 70 weight percent. The above Japanese Patent discloses a method for improving such a disadvantageous property of the modified acrylic fiber, namely, a method of spinning a dope of acrylic resin containing a certain amount of polymer of glycidyl methacrylate. The method is believed to be effective in preventing the devitrifying of the modified fiber.
Furthermore, regarding the light-proof property of acrylic fiber, kokai Japanese Pat. Pub. No. S.49 (1974)--7523 discloses the light-proof property of modacrylic synthetic fiber of vinylidene chloride series containing a large amount of halogen atoms in its molecular structure of copolymer as being rather inferior. It is generally believed that the most serious disadvantage of copolymers of acrylonitrile series containing halogen containing monomers is their easy color change when exposed to light or heat since the thermal stability and light-proof properties of such copolymer are poor. Moreover, there is the disadvantage of erosion and rusting of machines used for preparation of synthetic fibers from the copolymer. Moreover, rusting and erosion take place in spinning and weaving machines used for manufacturing spun yarn and clothes from such synthetic fibers.